Aim: Bronchioloalveolar carcinomas (BACs) are rare primitive lung adenocarcinomas growing along the alveolar septum without stromal, vascular or pleural invasion. We report an immunohistochemical study of their vascular microenvironment.
Methods and results: In three mucinous BACs (M-BAC) and three non-mucinous BACs (NM-BAC) we examined the following parameters in comparison with the normal lung: (i) constituents of the alveolar extracellular matrix; (ii) qualitative and quantitative changes of alveolar capillaries; and (iii) expression of vascular endothelial growth factor (VEGF) by tumour cells. In M-BAC, the alveolar matrix was unchanged compared with the normal parenchyma. Capillaries expressed normal alveolar endothelial markers and their average surface was calculated, as in normal lung, as 8%. VEGF was negative in tumour cells. In NM-BAC, the alveolar wall was thickened by deposits of fibronectin and type III collagen containing myofibroblasts and the basement membrane was disrupted. Capillaries did not retain alveolar endothelial markers and their surface was calculated as 19%. Tumour cells expressed high levels of VEGF.
Conclusions: In contrast to NM-BAC, M-BAC do not modify the alveolar structure and seem to exploit the normal alveolar vascular bed to grow, without inducing neoangiogenesis. A better understanding of the mechanisms of growth of lung cancers may have implications for future anti-angiogenic therapeutic strategies.